Humbucker
A conventional humbucker (or Humbucking pickup) is a type of electric guitar pickup that uses two coils, both generating string signal. Humbuckers have high output since both coils are in series and because the magnetic circuit is low loss. Since the two coils are of reversed polarity and reverse-wound and connected in series, noise and interference is significantly reduced via common-mode rejection. They get their name because they cancel out a large portion of the interference (they "buck the hum") induced by alternating current sources normally experienced with single coil pickups. History This first "humbucker" or humbucking pickup was the so-called PAF (literally "Patent Applied For") invented by Seth Lover, a Gibson employee, in 1957. Because of this, and because of its use on the Gibson Les Paul guitar, the humbucker is strongly associated with Gibson, although humbuckers have been used in many different guitar designs by many different manufacturers. Humbuckers are also known as dual-coil, double-coil, or hum-canceling pickups. Rickenbacker offered dual coil pickups arranged in a humbucking pattern beginning in late 1953 but dropped the design in 1954 due to the perceived distorted sound. The Gibson Les Paul was the first guitar to use humbuckers in substantial production, but since then, even some models of Fender Stratocasters and Telecasters, traditionally fitted with single-coil pickups, are factory-equipped with humbuckers. Stratocasters fitted with one humbucker in the bridge position, resulting in a pickup configuration noted as H-S-S (starting at bridge pickup: H for humbucker, S for single coil) are referred to as "Fat Strats", because of the "fatter", "rounder" tone offered by the humbucker pickup. How humbuckers work In any magnetic pickup, a vibrating soft-magnetic guitar string induces an alternating current in its coil(s). However, magnetic coils also make excellent antennas and are therefore sensitive to electromagnetic interference caused by mains wiring (mains hum) and electrical appliances like transformers, motors, and computer screens. Guitar pickups pick up this noise, which can be quite audible, sounding like a constant hum or buzz. A humbucker has two coils with opposing windings and polarities. The string motion induces current in both coils in the same direction. Electromagnetic interference, on the other hand, induces current in opposing directions in each coil because of the reversed winding and polarity. When the signals from both pickups are summed together, the noise is cancelled due to destructive interference, while the actual signal is increased due to constructive interference, thus dramatically improving the signal-to-noise ratio. This technique is called common-mode rejection by electrical engineers, and is also used in balanced lines in audio recording. Sound .]] Using two coils also changes the tone of the pickup. The humbucking pickup produces a "warm" and "fat" tone that has been popularly associated with Les Pauls and SGs, in contrast to the "bright" or "clear" tone of the single coil pickups that are typically used on Fender guitars such as the Stratocaster and Telecaster. However, there are humbucking pickups that have a bright tone, similar to that of single-coil pickups. It is a common misconception that because the coils are at slightly different positions along the string some of the higher-frequency harmonics are diminished or cancelled out, thus producing this warmer sound. This is only true if the pickup's coils are in reversed phase, (i.e., a phase switch on Vol/tone). The main reason humbuckers sound different is that the two coils resonate at different frequencies causing a broad resonant peak in frequency response, a characteristic of the original Gibson humbuckers, and because any two pickups wired in series will attenuate some of the higher frequencies due to the summed impedance. In fact, not all humbuckers have two separate full-size coils with two separate rows of magnetic pole pieces facing the strings; see the paragraphs below about "stacked" and "rail" designs. The "stack" and "rail" pickups can still produce the "warm" and "fat" tone, in spite of sensing only a small section of the string, just like single-coil pickups. Humbucker pickups are also available in single coil size. Usually, those who prefer the brighter sound of single-coil pickups had to simply live with the extra hum and buzz in order to get the tone they prefer, although technologies designed to preserve the tones exist. Alternative humbucker designs Stacked humbuckers Solid body guitars, such as Fender Stratocasters, usually feature cavities only for single-coil pickups. Installing full-sized humbuckers requires additional routing of the woodwork and cutting of the pickguard (if the instrument has a pickguard). If the process is not carefully done, the instrument's body and pickguard may be damaged and possibly affecting the tone produced by the body. This is unacceptable, especially for expensive vintage guitars where it is vital to preserve cosmetic appearance. As a result, many pickup manufacturers now produce humbucking pickups compacted into the size of a single coil, accomplished by vertically "stacking" the coils instead of placing them side-by-side as in a regular humbucker. Many different kinds of stacked humbuckers are available from several manufacturers, producing a wide range of different tones. Although the Fender Stratocaster-style single coil is by far the most frequently found pickup in a single coil size, humbuckers are available for most single-coil guitars. Fender produces several variations in their Telecaster, Jaguar, Jazzmaster, and Mustang guitars. Rail humbuckers Another design known as rail humbuckers divides a single coil-size pickup in half lengthwise, and the windings are wound around two pole pieces, typically resembling a rail. These pickups look like a normal, albeit smaller, humbucker. This, however, is typically used in conjunction with stacked humbuckers, to produce a high output pickup. This design can also extend to a "quadrail", by using a rail humbucker for each "single coil" of a normal humbucker. The same type of rails can also be found in a normal-size humbucker, however. Heavy metal guitarist Dimebag Darrell made heavy use of this type of pickup wired in the bridge position. These tend to also sound fuller and have a higher gain and attack than the single coil-size version. Coil splits Some guitars which have humbucking pickups feature coil splits, which allow the pickups to act as "pseudo-single" coils. The electrical circuit of the pickup is reduced to that of a true single coil while the magnetic circuit retains its original closed loop configuration. Usually, this feature is activated using a switch on the tone potentiometer. Coil split turns on when potentiometer is pulled out and reverts back off when it is pushed in. The resultant single coil sound is not the same as a Fender single coil sound because the poles of the coil are made of steel and not of alnico, and the coil turns are significantly less than a Fender pickup (5,000 as distinct to 8,000 - this can vary depending on the type and brand of the humbucker). :Note: this is often wrongly referred to as "coil taps". Coil taps are more commonly found on single coil pickups, and involve an extra hook-up wire being included during the manufacture of the pickup so the guitarist can choose to have all the windings of the pickup included in the circuit, for a fatter, higher output sound; or some of the windings in use and some "tapped off" for a brighter, lower output, cleaner sound.